A common challenge confronted in fabrication of polymer composites/nanocomposites is the efficient dispersion and high loading of fillers (nanofillers) in a thermoplastic.
Recent innovations in the field of polymer science and nanotechnology have led to the development of polymer nanocomposites. With incorporation of micro and nanoscale fillers of metals and metal oxides in regular polymer matrices improved functionalities, such as strength, toughness, wear resistance, fire retardance, and conductivity can be gained.
However, a common challenge confronted in fabrication of polymer composites/nanocomposites is the efficient dispersion of fillers/nanofillers in the thermoplastic. In a conventional practice, the thermoplastic is heated to a viscous melt and the nanofillers are dispersed in it by shear mixing. In this mixing process, the nanofillers have essentially zero diffusion in the viscous polymer matrix. In principle, the viscosity can be reduced at higher temperatures, but most thermoplastics are subject to rapid oxidation (i.e., combustion) at their melting temperatures, already. Inefficient dispersion of nanofillers results in aggregates, which then behave as micron-sized or larger particles. Consequently, the benefits inherent to nanoscale are lost, including high surface to volume ratio.
Alternatively, it is possible to take advantage of efficient dispersion of fillers/nanofillers in a solvent due to the unrestricted diffusion of micro/nanostructures in solvents. This approach allows efficient dispersion of the nanofillers in a polymer once that polymer is dissolved in the solvent. However, the desired polymer must be soluble in the same solvent as that of the nanofillers. Therefore, if the nanofillers are synthesized by solution chemistry, their solvent must be exchanged with a proper solvent, which also dissolves the polymer. This step is typically carried out by centrifuging or dialysis. Next, the polymer must be dissolved in the solvent. Depending on the polymer and solvent, the solution process may take from hours to days requiring heating and stirring. Finally, the solvent must be extracted by vacuum filtering or evaporation.
Therefore, although the approach of ‘solvent dispersion plus extraction’ works, it involves a number of arduous steps. Further, the use of solvents may be costly and involve health hazards. A need therefore exists for a method of fabrication of high dispersion polymer nanocomposites that can be conducted in an efficient manner that minimizes waste of costly solvents.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.